Who's winning F1's crucial diffuser war?

The efficiency of a Formula 1 car's diffuser is absolutely critical to getting the design to work. Who's coming out best on this front so far in 2018 testing?

On September 1 2017 the EU banned the sale of vacuum cleaners that used more than 900W of energy. This was down from somewhere around 2000W, so most people felt that was a bit harsh and it is possibly one of the reasons the UK is now trying to manoeuvre its way out of Europe!

The reason for all this was that most people felt this new regulation of using less power would mean the vacuum would be less powerful. But it turned out this was not so, as companies like Dyson just put extra effort into the detail design of the airflow and motor and came up with new machines that clean just as well using less power. The negative is they cost a lot more to purchase.